1. Field of the Invention
The present invention relates to ink jet printing devices, and more particularly, to a method of forming a charge plate for an ink jet printing device.
2. Prior Art
The present invention relates generally to ink jet printing devices of the type disclosed for example in Beam et al U.S. Pat. No. 3,586,907 and Mathis U.S. Pat. No. 3,701,998. These devices utilize charge plates which have a plurality of conductive rings aligned under the orifices from which the printing ink is expelled. An electrical charge is selectively established on each charge ring at an appropriate time to apply a charge on selected drops coming from the orifices. The selectively charged drops are subsequently deflected by an appropriately charged electrical deflection field into a catcher and thus prevented from impacting a recording medium while uncharged drops are unaffected by the electrical deflection field and thus impact the recording medium at the desired location.
Due to the fact that the charge rings formed about the orifices in the charge plate are very small in diameter, it is exceedingly difficult to fabricate such charge plates with the necessary accuracy of alignment to be in precise registry with the corresponding holes in the orifice plate. One method presently used for fabricating such charge plates employs a photo-chromic glass which is etched with the appropriate positioning of charge rings and leads extending to the circuit for individually charging each charge ring, the glass being fired to a ceramic state after etching in order to form the final charge plate assembly. However, this method is time consuming and not suffficiently repeatable to provide the high yield necessary for large volume production and in addition, the substrata generally used to support the charge rings, i.e. glass, is very fragile.